Secretion of adipokines by human adipose tissue in vivo: partitioning between capillary and lymphatic transport

Peptides secreted by adipose tissue (adipokines) may enter blood via capillaries or lymph. The relative importance of these pathways for a given adipokine might influence its biological effects. Because this has not been studied in any species, we measured the concentrations of seven adipokines and eight nonsecreted proteins in afferent peripheral lymph and venous plasma from 12 healthy men. Data for nonsecreted proteins were used to derive indices of microvascular permeability, which in conjunction with the molecular radii of the adipokines were used to estimate the amounts leaving the tissue via capillaries. Transport rates via lymph were estimated from the lymph adipokine concentrations and lymph flow rates and total transport (secretion) as the sum of this and capillary transport. Concentrations of nonsecreted proteins were always lower in lymph than in plasma. With the exception of adiponectin, adipokine concentrations were always higher in lymph (P < 0.01). Leptin and MCP-1 were secreted at the highest rates (means: 43 μg/h or 2.7 nmol/h and 32 μg/h or 2.4 nmol/h, respectively). IL-6 and MCP-1 secretion rates varied greatly between subjects. The proportion of an adipokine transported via lymph was directly related to its molecular radius (r(s) = +0.94, P = 0.025, n = 6), increasing from 14 to 100% as the radius increased from 1.18 (IL-8) to 3.24 nm (TNFα). We conclude that the lymph/capillary partitioning of adipokines is a function of molecular size, which may affect both their regional and systemic effects in vivo. This finding may have implications for the physiology of peptides secreted by other tissues.     

Comparative study of the changes in microanatomical organization of lymph nodes located and functioning in the area of venous congestion

By the morphometric method the microanatomical organization of the popliteal and kidney lymph nodes of the type Vi was studied in venous congestion. In the first experimental series (lymph nodes localize in venous congestion area) the venous congestion in the popliteal lymph nodes was created by the ligature of caudal vena cava. In the second experimental series (lymph nodes, which clean the venous congestion area--the kidney vena was tied up. The small and short time increase of the marginal sinus volume and hypertrophy of the medullary cords, which seemed about medullary substance B-zone stimulation were characteristically for the lymph nodes, localize in the venous congestion area. The sharp increase of the marginal sinus volume during the long experimental time and paracortical T-zone hyperplasia were characteristically for the lymph nodes, which clean the venous congestion area.     

Enzymatic differentiation of arterial and venous segments of the capillary bed during the development of free muscle grafts in the rat

The revascularization of freely grafted muscles in the rat was studied by histochemical reactions that on frozen sections stain the arterial part of the capillary bed blue (alkaline phosphatase [AP] reaction) and the venous part of the capillary bed red (dipeptidyl peptidase IV [DPP IV] reaction). In 112 rats the extensor digitorum longus or soleus muscles were freely grafted and removed at various times up to 93 days following the surgery. In cross section, the capillaries of a normal muscle show a mosaic pattern of staining for the activity of the two enzymes. After grafting, DPP IV activity of capillaries is lost throughout the entire graft within a day or two; but within ischemic muscle, weak and diffuse AP staining persists in capillary remnants for up to 6 days. In the very periphery of the graft AP staining is also preserved in partially damaged capillaries. By 4 days, new AP-positive capillaries can be identified at the periphery of the graft, and in succeeding days AP-positive capillaries are found progressively nearer the center of the graft. At 7 days, the capillary/muscle-fiber ratios are 66% of normal in the periphery of the graft and 44% in the intermediate zone. DPP IV-stained capillaries are not seen until 7 days after grafting. By 60 days, when the grafts have become stabilized, the mosaic pattern of capillary staining has become reestablished. In mature grafts, the number of capillaries per unit area was slightly higher than that in control muscles, but the capillary/muscle-fiber ratio was slightly lower, owing to the smaller than normal cross-sectional areas of the regenerated muscle fibers.     

Stimulation of rapidly adapting pulmonary stretch receptors by pulmonary lymphatic obstruction in dogs

The effects of pulmonary lymphatic obstruction and pulmonary venous congestion on the activities of slowly adapting receptors (SAR) and rapidly adapting receptors (RAR) of the airways were examined in anaesthetized, artificially ventilated dogs. In 11 out of 12 RAR (12 dogs) examined, pulmonary lymphatic obstruction for a period of 20 min produced a sustained significant increase in activity without a significant change in peak airway pressure and dynamic compliance. The activity remained significantly elevated even after the pulmonary lymphatic obstruction was released. This stimulus was without effect on the SAR (n = 5 dogs). Pulmonary venous congestion alone increased the RAR activity (n = 7 dogs) significantly without producing significant changes in airway mechanics. Lymphatic obstruction, when superimposed upon congestion, did not produce a further significant increase in activity. In four dogs the effect of pulmonary venous congestion (left atrial pressure increased from 7.6 +/- 1.7 to 16.3 +/- 2.7 mmHg) (1 mmHg = 133.3 Pa) on pulmonary lymphatic flow was examined. The procedure caused a significant increase in lymph flow. These results suggest that in the dog, the RAR activity is influenced by changes in the pulmonary extravascular space.     

Ultrastructural organization of the endotheliocytes of iliac lymph node capillaries in pregnancy (morphometric study)

Using light and electron microscopy and morphometry, the morphological changes in the lymph nodes of arterial and venous parts of capillaries were studied on the 11th, 17th and 21st days of pregnancy in rats. Ultrastructural changes in endothelial cells of blood vessels in the uterine lymph nodes during normal pregnancy are of adaptive nature and are possibly responsible for the relief of the blood congestion in the system of the inferior vena cava and for the improvement of the utero-placental circulation.     

Flow and composition of lymph from the ovary and uterus of cows during pregnancy

Ovarian or uterine lymph was collected continuously for periods of up to 25 days from 16 cows cannulated at stages of pregnancy ranging from 96 to 278 days post coitum. Blood samples were taken acutely from the ovarian and uterine veins during surgery and periodically from the jugular vein during the course of lymph collection. The flow rate and cell content of lymph was measured and blood and lymph plasma samples were analysed for progesterone, pregnenolone, pregnenolone sulphate, androstenedione, testosterone, oestrone, oestrone sulphate, oestradiol-17 beta, prostaglandin (PG) F-2 alpha, total protein and albumin. There was a high flow rate of protein-rich lymph from luteal ovaries with rates up to 101.7 ml/h occurring in individual lymphatics over short periods. Peripheral ovarian and uterine lymph contained a low concentration of cells (mean less than 10(5) cells/ml) comprising about 82-87% lymphocytes, 11-14% macrophages and monocytes and 2-4% other cells. At all stages of pregnancy, the concentration of progestagens and androgens was higher in ovarian lymph than in uterine lymph or blood plasma. The differences were greatest for progesterone and androstenedione which occurred at 200-fold and 60-fold greater concentration respectively in ovarian lymph than in jugular plasma. When serial 10 min samples were collected over a 12-h period, the concentration and output of progesterone in ovarian lymph varied in a phasic manner, ranging from 3.5 to 7.6 microM and from 31.7 to 293.1 nmol/h respectively. There was a positive correlation between the output of progesterone in lymph and the progesterone concentration in jugular blood samples taken every 20 min. During most of pregnancy there was little difference between the concentration of oestrogens in ovarian lymph, ovarian venous plasma and jugular plasma but, during the 3-5 days before calving, these hormones occurred at slightly higher concentration in ovarian lymph. Apart from pregnenolone and androstenedione, all steroids occurred at lower concentrations in uterine lymph than in jugular plasma. Shortly before parturition there was an abrupt increase in the concentration of PGF-2 alpha in uterine lymph. Lymph reflects more accurately the milieu of tissue cells than efferent blood and further analysis of differences in the concentration of substances in lymph relative to the output in the ovarian and uterine arterial and venous blood may lead to the identification of factors important in local regulatory mechanisms in the reproductive tract.     

Lymphatic transport of cellular enzymes from muscle into the intravascular compartment.

In an experimental study, employing anaesthetized dogs, it was investigated whether cellular enzymes from peripheral skeletal muscle get into the circulating blood by diffusion across capillary membranes or by lymphatic transport. In the experimental group 1, the animals were anaesthetized only. The plasma activities of the four enzymes measured--lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, creatine kinase--did not show any mentionable change during a time period of 6 h. In group 2 one hind limb of each animal was moved passively for 1 h. Alanine aminotransferase remained unchanged in plasma, the activities of the three other enzymes increased significantly. In group 3 one hind limb was made hypoxic by clamping the femoral blood vessels for 1 h. No activity changes were observed. When the period of hypoxia was followed by a 1-hour period of passive movement in group 4, the alterations in plasma activities were almost identical to those observed in group 2. In group 5 the experimental procedure was as in group 4, in addition the lymph from the thoracic duct was quantitatively withdrawn. The enzyme activities in plasma revealed a tendency to decrease rather than increase. Lymph flow increased significantly as well as the lymphatic activities of those enzymes which have high intracellular activities in muscle. The results prove, that enzymes from muscle are transported from the interstitial into the intravascular compartment mainly by lymphatic transport. Indications were found that the interruption of blood flow in one hind limb did not result in an enzyme release from muscle cells. It is discussed how changes in lymph flow, occurring during physical exercise for example, affect enzyme activities in plasma.     

Morphometric study of the ultrastructural organization of the endotheliocytes of blood capillaries in the iliac lymph nodes of pregnant rats

The ultrastructure of blood capillary endotheliocytes of iliac lymph nodes during pregnancy was investigated in rats. It was found that changes in microcirculation during pregnancy are accompanied by the appearance of the adaptive changes at all levels of lymph node structural organization. They are: increased lumen of arterial and venous part of the capillaries, increased intermediate sinus volume, increased fenestration of both parts of capillaries, a sharp increase in the number of micropinocytous vesicles and activation of transendothelial channel formation.     

Enzymatic heterogeneity of the capillary bed of rat skeletal muscles

This study of the capillaries in rat skeletal muscle involved the use of a histochemical method that allows one to distinguish between arterial and venous portions of capillaries. Under controlled staining conditions, the arterial portion of the capillary bed reacts positively for alkaline phosphatase (AP) activity, and the venous portion is positive for dipeptidyl peptidase IV (DPP IV) activity. A short transitional capillary segment is positive for the activity of both enzymes. Capillaries of the normal soleus muscle and the red and white portions of the sternomastoid muscle have been quantitatively analyzed. Quantitative data demonstrated differences in capillary dimensions among the muscles studied. Capillaries of the white part of the sternomastoid were the longest, and they had the shortest DPP IV-positive segment (8% of the total capillary length). Capillaries of the soleus muscle were the shortest, and they also had short DPP IV-positive segments (16%). In contrast, the DPP IV-positive segments of the red part of the sternomastoid occupied 60% of the total capillary length. Survey cross sections reveal a mosaic distribution of patches of capillaries stained for AP and DPP IV activity. This study reveals that within given bundles of muscle fibers, the capillaries that run parallel to the muscle fibers are aligned relative to one another in such a manner that their arterial and venous segments are in register.     

Factors regulating the formation of chylomicrons and very-low-density lipoproteins by the rat small intestine

The aim of this study was to investigate how the relationship between chylomicron and very-low-density lipoprotein (VLDL) transport of fatty acid into lymph was affected by the total amount of lipid transported via the intestinal lymphatics in the rat. Two different experimental conditions were employed. First, intestinal lymph fistula rats were infused with four different levels of [3H]oleic acid (15, 30, 60 and 120 mumol per h) at a constant rate for 8 h. Lymphatic transport of [3H]oleic acid via chylomicrons and VLDLs was measured in lymph collected during the seventh h. Within the dose range studied chylomicron increased exponentially, while the output in VLDL reached a plateau at a total lymph [3H]oleic acid output of approx. 60 mumol/h. A linear regression analysis of the ln(chylomicron/VLDL) versus the total output in lymph yielded a coefficient of correlation of 0.95. Second, we utilized the fact that intraduodenal infusion of the nonionic detergent Pluronic L-81 (L-81) inhibits chylomicron transport and that this inhibition is reversed by the cessation of L-81 infusion (unblocking). A linear regression analysis of the ln(chylomicron/VLDL) versus total lymph [3H]oleic acid output during the first 4 h of unblocking gave a coefficient of correlation of 0.79. Statistical analysis of the regression equations from the two experiments showed that for the same lymphatic [3H]oleic acid output, the chylomicron/VLDL ratio was significantly lower in the L-81 experiment, indicating that the relative rates of formation of chylomicron to VLDL were different under these two experimental conditions. However, the principal pattern was the same, i.e., chylomicron production increased, while VLDL production became saturated when the amount of oleic acid transported to the lymph was increased.     

Use of a microtensiometer technique to study hydraulic lift in a sandy soil planted with pearl millet (Pennisetum americanum [L.] Leeke)

A pot experiment was carried out with pearl millet (Pennisetum americanum [L.] Leeke) growing in a sandy soil in which the upper (topsoil) and lower (subsoil) parts of the pots were separated by a perlite layer to prevent capillary water movement. Using microtensiometers a study was made to establish whether it was possible to measure hydraulic lift by which the upper part of the soil was rewetted when water was supplied exclusively to the lower part of the soil.Hydraulic lift occurred during the first seven days of the period of measurement, with a maximum water release to the soil of 2.7 Vol. % during one night (equivalent to 10.8 mL water in the top 10 cm of the soil profile). This magnitude was obtained at very high root length densities, so that water release from the roots would be expected to be much smaller under field conditions.Hydraulic lift ceased when the soil matric potential in the topsoil dropped below-10 kPa at the end of the light period and could not be re-established, neither by extending the dark period, nor after rewatering the topsoil. The disappearance of hydraulic lift could be explained in part through osmotic adaptation of plant roots and, thus prevention of water release from the roots in the topsoil. It is concluded that hydraulic lift may affect nutrient uptake from drying topsoil by extending the time period favourable for uptake from the topsoil.     

Comparison of Three Screening Test Kits for G6PD Enzyme Deficiency: Implications for Its Use in the Radical Cure of Vivax Malaria in Remote and Resource-Poor Areas in the Philippines

Objective

We evaluated a battery of Glucose-6-Phosphate Dehydrogenase diagnostic point-of-care tests (PoC) to assess the most suitable product in terms of performance and operational characteristics for remote areas.

Methods

Samples were collected in Puerto Princesa City, Palawan, Philippines and tested for G6PD deficiency with a fluorescent spot test (FST; Procedure 203, Trinity Biotech, Ireland), the semiquantitative WST8/1-methoxy PMS (WST; Dojindo, Japan) and the Carestart G6PD Rapid Diagnostic Test (CSG; AccessBio, USA). Results were compared to spectrophotometry (Procedure 345, Trinity Biotech, Ireland). Sensitivity and specificity were calculated for each test with cut-off activities of 10%, 20%, 30% and 60% of the adjusted male median.

Results

The adjusted male median was 270.5 IU/10¹² RBC. FST and WST were tested on 621 capillary blood samples, the CSG was tested on venous and capillary blood on 302 samples. At 30% G6PD activity, sensitivity for the FST was between 87.7% (95%CI: 76.8% to 93.9%) and 96.5% (95%CI: 87.9% to 99.5%) depending on definition of intermediate results; the WST was 84.2% (95%CI: 72.1% to 92.5%); and the CSG was between 68.8% (95%CI: 41.3% to 89.0%) and 93.8% (95%CI: 69.8% to 99.8%) when the test was performed on capillary or venous blood respectively. Sensitivity of FST and CSG (tested with venous blood) were comparable (p>0.05). The analysis of venous blood samples by the CSG yielded significantly higher results than FST and CSG performed on capillary blood (p<0.05). Sensitivity of the CSG varied depending on source of blood used (p<0.05).

Conclusion

The operational characteristics of the CSG were superior to all other test formats. Performance and operational characteristics of the CSG performed on venous blood suggest the test to be a good alternative to the FST.     

Acute effects on the lung and the liver of oral administration of cerium chloride on adult, neonatal and fetal mice

We evaluated tissue changes associated with cerium chloride administration via gavage to adult mice, via milk to neonatal mice and transplacentally to fetal mice. Change in adults consisted of extensive pulmonary hemorrhage, pulmonary venous congestion, thickened alveolar septae, hepatic necrosis and neutrophil infiltrations. Those in fetal mice consisted of pulmonary and hepatic congestion. These results indicate that gavage cerium administration elicited subtle tissue changes, though oral toxicity is rather low. These changes were less severe in neonatal and fetal mice. When cerium was injected into adult mice through the tail vein, cerium was distributed mainly to the liver, spleen and lung dose-dependently with the cerium concentration gradually decreasing after 3 days. A study of cerium anticoagulation in mouse plasma showed that clotting time was significantly prolonged when cerium was added to plasma. These results suggest that cerium may disturb blood coagulation and cause pulmonary and hepatic vascular congestion.     

Alteration by Diacylglycerols of the Transport and Fatty Acid Composition of Lymph Chylomicrons in Rats

Lymph fistula rats were continuously infused with emulsions containing diacylglycerol consisting of 1,3-species (65.6%), 1(or 3),2-species (32.6%), and triacylglycerol (rapeseed oil) at the rate of 3ml/h for 1 h through a cannula inserted into the stomach. The lymph fluids were collected every hour for 5 h after starting the infusion of the lipid emulsions, and the lymph chylomicrons were isolated, purified and analyzed. Test emulsions were prepared to provide the same amount of fatty acids (144mg/h) as that in these acylglycerols. The rates for triacylglycerol transport at 2–3 h and for cholesterol transport by chylomicrons at 2–3 h and 3–4 h of the experimental period in rats infused with the diacylglycerol emulsion were significantly lower than the corresponding values in the rats infused with the triacylglycerol emulsion. As a consequence, the cumulative value for triacylglycerol transport at the end of the experimental period in rats infused with the diacylglycerol emulsion was significantly lower than the corresponding value in the rats infused with the triacylglycerol emulsion. In addition, cumulative values for cholesterol transport from 3h to the end of the experimental period were significantly lower in the former than in the latter. There was no difference in the total fatty acid compositon of chylomicron-triacylglycerol between the rats receiving the triacylglycerol and diacylglycerol emulsions. However, a considerable difference existed in the fatty acid composition at the 2-position of triacylglycerol between the two groups of rats. Thus, intragastric infusion of diacylglycerol mainly consisting of the 1,3-species compared to triacylglycerol not only altered the rate of lipid transport by lymph chylomicrons but also altered the structure of the triacylglycerol moiety in the rats.     

Littoral cells of the lymph node sinuses in venous congestion based on scanning electron microscopic data

The littoral cells of the sinuses in the popliteal lymph nodes have been studied in Wistar rats under physiological conditions of hemodynamics and 1 h after ligation of the caudal vena cava. Intercellular clefts (1-4 mcm wide) are demonstrated to exist between the littoral cells of the internal wall of the marginal sinus. Presence of fenestrae in the peripheral thinned areas of cytoplasm is specific for these cells. The diameter of the fenestrae is 60-1,000 nm however, the fenestrae with the diameter up to 100 nm predominate. Lining of the medullar sinuses is also characterized by a high content of fenestrae, the maximal diameter of the fenestrae being the same as in the marginal sinus, although most of the fenestrae have the diameter 50-500 nm. No open intercellular clefts between the littoral cells of the medullar sinuses are revealed. In some cases, penetration of lymphocytes through the lining of the sinuses is observed. Under venous congestion, the diameter and amount of the fenestrae, size and amount of open intercellular clefts in the lining of the lymphatic sinuses increase significantly. This demonstrates its increasing permiability, having an essential importance for compensation of circulatory disturbances in the zone of the venous congestion.     

Enzyme activities in thoracic duct lymph and plasma of anaesthetized, conscious resting and exercising dogs

The significance of changes in lymph flow for the extracellular distribution and transport of cellular enzymes and for the level of enzyme activities in plasma was investigated. Specimens of thoracic duct lymph were obtained from an extracorporal lymph shunt in anaesthetized, conscious resting and treadmill exercising dogs (6 km X h-1 for 1 h) The activity of 10 enzymes and of protein content in lymph and plasma were studied, as well as lymph flow, lymphatic transport, and the lymph-plasma ratio of these compounds. Lactate, pH, and blood gases were monitored in venous blood. Lymph flow of 0.80 ml X min-1 in anaesthetized dogs more than doubled (to 1.86 ml X min-1) when the animals were conscious and resting. In anaesthetized dogs lymph enzyme activity was higher only for enzymes of predominately hepatic origin, such as choline esterase (CHE) and alanine aminoferase (ALAT), and was lower for aspartate aminotransferase (ASAT) and aldolase (ALD). In conscious dogs, due to activation of the skeletal muscle "tissue pump", lymphatic transport of enzymes with rather high activity in skeletal muscle, and of protein, is significantly enhanced. Enzyme activities in plasma, however, did not differ between the groups. Lymph-plasma activity ratios higher than one were found for lactate dehydrogenase (LDH), malate dehydrogenase (MDH), ASAT, creatine kinase (CK), ALD, and phosphohexose isomerase (PHI). Exercise stimulated lymph flow up to 4.9 ml X min-1, and increased the lymphatic activities of those enzymes with a lymph-plasma ratio higher than unity, these enzymes increasing in the plasma due to the highly increased lymphatic transport.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diaphragmatic O2 and lactate extraction during submaximal and maximal exertion in ponies

Diaphragmatic O2 and lactate extraction were studied in 10 healthy ponies at rest and during treadmill exercise. The phrenic vein was aseptically catheterized via a lateral thoracotomy 8-35 days before the study. Arterial and phrenic venous blood samples were obtained simultaneously at rest and at 30-s intervals during 4 min of exertion. Three levels of exertion were studied (moderate, 10 mi/h; heavy, 15 mi/h; maximal, 20 mi/h), and a rest period of at least 90 min was allowed between them. Each pony was studied twice at least 2-3 days apart. At rest the diaphragmatic venous PO2, O2 saturation, arteriovenous O2 content difference, and O2 extraction were 43.2 +/- 2.0 Torr, 76.1 +/- 3.2%, 3.14 +/- 0.43 ml/dl, and 23.60 +/- 3.61%, respectively. Significant decrease in phrenic venous PO2 and O2 saturation occurred within 30 s of exercise. Phrenic venous PO2 decreased to 20.3 +/- 1.0, 18.9 +/- 1.1, and 15.4 +/- 0.9 Torr at 120 s of moderate, heavy, and maximal exercise, respectively. Corresponding values of phrenic venous O2 saturation were 33.6 +/- 2.2, 25.8 +/- 2.1, and 17.9 +/- 0.5%, respectively. Diaphragmatic arteriovenous O2 content difference expanded to 13.11 +/- 0.49, 15.00 +/- 0.60, and 16.90 +/- 0.60 ml/dl at 120 s of moderate, heavy, and maximal exercise, respectively, as O2 extraction rose to 65.93 +/- 1.98, 73.90 +/- 1.99, and 80.95 +/- 0.47%, respectively. During heavy and maximal exercise, the diaphragmatic venous lactate concentration remained similar to the arterial concentration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Albumin transport across pulmonary capillary-interstitial barrier in anesthetized dogs

To evaluate albumin transport across the pulmonary capillary endothelial and interstitial barriers, we simultaneously measured blood-to-tissue (QA,t) and blood-to-lymph (QA,l) clearances of 125I-radiolabeled albumin as well as endogenous albumin clearance (Qa,l) in the canine lung in vivo (n = 10). Steady-state prenodal lung lymph flows (Qw,l) and protein clearances were measured over a 2-h period at a constant capillary pressure (Pc, 13-33 cmH2O). Comparison between QA,t and QA,l as a function of Pc suggests that little of the albumin that crossed the capillary wall remained in the lung tissue, with most leaving in the lymph. Qw,l increased significantly as Pc increased, but lung tissue water was minimally affected. From the ratio of the clearance-Pc slopes for albumin and water, the albumin reflection coefficient was estimated to be 0.81 using QA,l and Qw,l and 0.56 using Qa,l and Qw,l. The permeability surface area product for the sum of blood-to-tissue and blood-to-lymph fluxes of labeled albumin (QA,t + QA,l) was 31 +/- 9 microliters/min, whereas that calculated from the blood-to-lymph flux of endogenous albumin (Qa,l) was 97 +/- 22 microliters/min. These data suggest that 1) both tissue and lymph accumulations of albumin must be considered when microvascular permeability is evaluated using protein tracers; 2) lymph clearance, but not tissue accumulation of albumin, was filtration dependent; and 3) lymph flow was an important contributor to the safety factor against edema formation over a moderate range of capillary pressures.     

Zinc transport by transferrin in rat portal blood plasma.

Zinc transport in mesenteric lymph and zinc distribution in portal plasma and venous plasma were examined in rats that had been given an oral dose of ⁶⁵Zn. Less than 1% of an oral dose of ⁶⁵Zn appeared in the mesenteric lymph over a period of 8 hr. In portal plasma, approximately 70% of the isotope recovered after gel-filtration chromatography was bound to a protein that was identified as transferrin on the basis of molecular weight and electrophoretic properties. In venous plasma, the major fraction of ⁶⁵Zn was bound to albumin while the remainder of the isotope was associated with higher molecular weight proteins including transferrin and α₂-macroglobulins. These results demonstrate that zinc is transported from the intestine to the liver via the portal blood, and the results demonstrate that zinc is transported in portal plasma bound to transferrin.     

DNA Synthesis in Microspores in Anther Culture of Wheat (Triticum aestivum L.)

Anthers with mid-unlnucleate microspores were cultured on W5 medium supplemented with 0.5 mg/l kinetin, 2 mg/l 2,4-D and 9% or 3% sucrose. At a series of interval (0, 1, 1.5, 2, 14 days) after cultured, the anthers were labelled with 3H-thymidine (4 MCi/mi) for 24 h, fixed, and then performed autoradiography according to conventional method. Results show that after cultured for 24 h, 3H-thymidine was incorporated into some late-uninucleate microspores (see Plate I, 3), and after for 2.5 days, vegetative nuclei in pollen grains were la- belled (see Plate I, 4). Usually, vegetative nuclei were labelled frequently and generative ones were labelled rarely. Sometimes generative cell which could synthesis DNA might develop suspensor-like structure individually (see Plate I, 13). During early stage of development of a multicellular pollen grain, the DNA synthesis in the cells were synchronized. With pollen development, the synchronism of DNA synthesis was destroyed. When anthers cultured on medium with 3% sucrose, DNA in microspores could be synthesized normally, and the number of labelled microspores was more than that of anthers cultured on medium with 9% sucrose. However, on medium with 3% sucrose, the nuclei in microspores stopped dividing after one or two divisions and the cell wall of them could not be formed and multicellular pollen was not observed. It seems that the absence of multicellular pollen on medium with 3% sucrose was primarily due to the block of cell division and cell wall formation, not due to the interruption of DNA synthesis.